71.1 Friday, Jan. 6 Transoceanic migratory dispersal in young sea turtles: the role of currents and geomagnetic navigation PUTMAN, N.F.*; VERLEY, P.; SHAY, T.J.; LOHMANN, K.J.; North Carolina State University; IRD - Sete, France; UNC Chapel Hill; UNC Chapel Hill firstname.lastname@example.org
Upon hatching, young sea turtles immediately migrate offshore and into ocean gyre systems that promote long-distance transport. Because young turtles are often characterized as weak swimmers, or as inactive, their distribution in the open-sea is thought to be dependent on prevailing currents. In contrast to this view, lab-based experiments demonstrate that newly hatched loggerhead turtles from Florida, USA orient their swimming direction in response to regional magnetic fields that exist in the North Atlantic Subtropical Gyre. These findings imply that young turtles engage in directed swimming in the open-sea. However, whether this behavior influences the dispersal trajectories and ocean basin-scale distribution of young turtles is unknown. To address this question, numerical experiments were performed using particle-tracking software that coupled empirical observations of magnetic orientation by turtles to an ocean circulation model. Results revealed that even moderate amounts of swimming in response to magnetic fields resulted in substantial differences in dispersal trajectories compared to scenarios of passive drift. Turtles that engaged in magnetic navigation behavior were more likely to encounter productive foraging areas, remain within warm-water currents favorable for growth and survival, avoid areas on the perimeter of the gyre where predation risk and thermal conditions pose threats, and successfully return to the gyre if carried into coastal areas. These findings imply that marine animals traditionally viewed as ineffective swimmers may be able to exert unexpectedly strong effects on their dispersal trajectories and open-sea distributions by relying on a simple navigation strategy and minimal swimming.